Shaikhul-Islam Ibn Taymiyyah rahimahullah was asked:
A man leads the people in prayer and he recites with the recitation of Shaikh Abu ‘Amr. Is he sinful or is his prayer invalid or rejected, if he recites in Warsh or Nafi’, along with the difference in the recitations, and him reciting with the recitation of Abu ‘Amr [mainly] in the prayer?
“It is allowed for him to recite some of the Quran in the recitation of Abu ‘Amr and some of it in the recitation of Nafi’, whether that is in one rak’ah or two rak’ahs and whether that is outside of the prayer or inside the prayer. And Allah Knows Best”
[Majmoo’ al-Fatawa (22/445)]
Faisal Ibn Abdul Qaadir Ibn Hassan